The present invention generally relates to a method for reducing biofilm coatings and similar organic deposits in water systems. More particularly, the present invention is directed to an amine-formaldehyde condensate, optionally blended with surfactants in order to provide a composition useful as a biodispersant in cooling water systems. The composition can be used for preventing slime masses which result from bacterial, fungal, or algal growth. The elimination of such growth maintains water contact surfaces in a growth-free state and results in improved heat transfer efficiency of the equipment. In addition, water re-circulation lines, pumps, and reservoirs associated with the cooling equipment are maintained in a growth free state. The reduction in biofilm deposits also helps in the control of scale and corrosion. Further benefits include more effective control of pathogenic organisms such as Legionella pneumophila, which has caused outbreaks of Legionnaire""s disease attributed to contaminated water cooling systems. The products of this invention will generally be used in conjunction with oxidizing and/or non-oxidizing biocides to affect a microbial control treatment regimen.
In the past, others have attempted to suppress biofilm growth and production from cooling water systems. For instance, U.S. Pat. No. 4,673,509 to Davis et al., which is incorporated herein by reference, discloses a method for treating water systems which are susceptible to biofilm growth. In Davis et al., hydroxy alkyl phosphorus compounds are used to control aquatic growth and films in process water systems. U.S. Pat. No. 4,976,874 to Gannon et al., incorporated herein by reference, discloses a method and formulation for the control of biofouling using an oxidizing halogen in combination with a non-oxidizing quaternary ammonium halide. U.S. Pat. No. 5,866,016 to Jacquess et al., incorporated herein by reference, teaches a method for controlling biofouling with a combination of ionene polymers with salts of dodecylamine, where the ionenes are classified as quaternary ammonium polymers.
As will be clear from the description which follows, there remains room for improvement and variation within the art.
In general, the present invention is directed to a process for the control of biological and other organic containing deposits in industrial cooling and process waters. Very generally, the composition of the present invention relates to materials that, when applied to cooling waters, remove biofilms and control their growth. At higher concentrations, the material provides a successful treatment formulation for existing contamination, followed by subsequent control through lower maintenance doses.
The present invention recognizes and addresses the problems associated with the control of biofilms and biological growth within industrial cooling and waste water. Accordingly, it is an object of the present invention to provide a biofilm control composition. It is another object of the present invention to provide a method of controlling the formation of biofilms in industrial cooling and process water systems. It is yet a further object of this invention to limit the surface attachment of microorganisms, which leads to the biofilms on surfaces of water system equipment. Another object of the present invention is to provide a biofilm control composition and method that is compatible with existing chemical treatments for corrosion inhibition, scale and mineral deposits, as well as with biocides, both oxidizing and non-oxidizing.
These and other objects of the present invention are achieved by providing a composition for removing and preventing biofilms in industrial cooling and process water systems. The composition includes an amine-formaldehyde condensate optionally with a surfactant. The inclusion of from about 0.1% to about 10% of a surfactant to the amine-formaldehyde condensate also provides a highly effective composition which has been found useful for the control of aqueous bacterial, algal, and fungal deposits.
It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary construction.
The present invention is directed to a composition and method for the control of biofilms. As used herein, the term biofilm refers to organic films and deposited matter resulting from metabolic activity of biological organisms. Control of the biofilms means the prevention or substantial reduction of biofilm formation. The term xe2x80x9ccontrolxe2x80x9d also refers to the ability to slow the development of a biofilm by the use of the present invention, compared to a system or application without the present invention. As used herein, the term xe2x80x9ccontrolxe2x80x9d also includes treatments designed to eliminate or substantially reduce established biofilms. Once treated, the present invention is further capable of controlling additional biofilm formation through maintenance protocols as established herein.
More specifically, an amine-formaldehyde condensate made from 1-95% by weight of amine selected from the group comprising dicyandiamide, guanamines, guanidine, melamine, aniline, urea, thiourea, cyanamide, and guanylurea, combinations and salts or derivatives thereof; 0-20% by weight of an alkylenepolyamine selected from alkylamines, alkyldiamines, alkenepolyamines, alkanolamines, and combinations thereof; 1-98% by weight of an inorganic or organic acid, optionally neutralized with ammonium hydroxide or alkali; 1-98% by weight of formaldehyde or its precursors/donors; and 0-10% by weight of a surfactant is an effective composition. Aminopolymers such as those referenced above constitute a well-known class of compounds as described in Organic Polymer Chemistry, 2nd ed., Chapman and Hall, 1988, pp. 341-357, and incorporated herein by reference.
More specifically, the amine-formaldehyde condensates which are most effective are the reaction product of an amino base, a formaldehyde, an alkylenepolyamine, and the ammonium salt of an inorganic or organic acid. Condensates of this type are well known and are described in U.S. Pat. Nos. 3,106,541, 3,410,649, 3,582,461, and 4,383,077, the disclosures of which are incorporated herein by reference. Exemplary amino bases are dicyandiamide, guanamines, guanidine, melamine, aniline, urea, thiourea, cyanamide, guanylurea, and combinations thereof.
The formaldehyde component may be obtained from aqueous solutions or in polymeric or bound form such as paraformaldehyde, trioxane, hexamethylenetetramine, an acetal, or other formaldehyde donor.
The alkylenepolyamine is selected from the group comprising ethylenediamine, propylenediamine, butylenediamine, pentylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,2-propylenediamine, dibutylenetriamine, tributylenetetramine, tetrabutylenepentamine, dipentylenetriamine, tripentylenetetramine, tetrapentylenepentamine, alkanolamines, and combination isomers, oligomers, or polymers thereof.
The ammonium salts of acids may be formed prior to introduction to the other reagents or formed in situ by reacting the corresponding acid such as hydrochloric, sulfuric, phosphoric, boric, formic, acetic, glycolic, propionic, butyric, and the like with ammonium hydroxide or ammonia.
Optionally, a cationic and/or nonionic surfactant may be blended or reacted with the condensate polymer described above. The surfactant may contain low levels of anionic groups but are predominantly cationic or nonionic in charge. The cationic surfactant is preferably a quaternary ammonium halide compound, and more preferably an alkyldimethylbenzylammonium chloride wherein the alkyl group consists of between 8 and 22 carbon atoms (Barquat, Lonza, Inc.). The nonionic surfactants include condensation products of ethylene oxide and/or propylene oxide with hydrophobic materials such as fatty alcohols or alkylphenols (Tergitol, Union Carbide), and ethylene oxide copolymers with propylene oxide (Pluronic, BASF).
In addition to the acid condensation products described above, it is also possible to use amine-formaldehyde condensation products made at a neutral or alkaline pH. Examples of such condensation products may be found in reference to U.S. Pat. No. 3,015,649 which is incorporated herein by reference.
Suitable amine formaldehyde condensation products made at a neutral or alkaline pH may be provided from a mixture of dicyandiamide, urea, and formaldehyde along with a solubilizing agent added before, during, or after the condensation. Preferably, the solubilizing agent is anionic, water-soluble, and is a substantially neutral or alkaline salt of aromatic or C-10 or higher aliphatic sulfonic acids and their derivatives. Suitable examples include the sodium, potassium, lithium, ammonium, or other alkali metal salt of naphthalene sulfonic acid, dinaphthyl-methane disulfonic acid and their derivatives, and other water-soluble salts of sulfonic acid as referenced in U.S. Pat. No. 2,737,504 which is incorporated herein by reference.
The formulas and reactions described above were used with the materials listed in the following product examples to provide the biocidal compositions. The biocidal compositions were then used as described in the working examples which follow. The following examples and embodiments are intended to illustrate, not limit, the invention.